Switchgear are known which, when certain predefined electrical states occur in a line leading through the switchgear, automatically open the switching contacts of the switchgear and interrupt the flow of current in the line in this way. Switchgear of this type is referred to as an automatic circuit breaker or circuit-protection device. In order to detect short circuits and to rapidly break a line in the event of a short circuit, electromagnetic tripping devices that comprise a coil in which an armature is movably arranged are known and standard. In the event of a short circuit, a magnetic field is generated in the coil which causes the armature to move, which in turn causes the switching contacts of the switchgear in question to open.
When interrupting a current, an arc is produced between the switching contacts that are being separated. This arc is very pronounced, particularly at high currents that prevail in the event of a short circuit. Circuit-protection devices therefore generally comprise an arc quenching apparatus. The circuit breaker is therefore generally shaped in the region of a contact point of the switching contacts such that an arc produced when the current is interrupted is, or is intended to be, guided or conveyed away from the contacts and into the arc quenching apparatus. Since an arc is an electrical conductor, a magnetic field has an effect on said arc. In known switchgear, particularly in the event of a short circuit being tripped, it has been shown that the arc may be negatively affected by magnetic fields in the switchgear, and said effect may be such that the arc is prevented from migrating from the switching contacts towards the arc quenching apparatus. As a result, the arc is not quenched, and therefore the flow of current through the switchgear is not interrupted either. In addition to a complete failure of the switchgear, this may also lead to injury to persons and damage to equipment.